This invention relates to the preparation of N-substituted piperazinones. More specifically, it pertains to a process for preparing N-substituted piperazinones by reacting a substituted diamine with an aldehyde.
The piperazinones prepared by this invention are useful as catalysts for the hydrolysis of carbon oxysulfide which is a toxic contaminant found in petroleum refinery gases and coal gasification product streams. Piperazinones are also useful for extracting hydrogen sulfide and lower alkyl mercaptans from various industrial gas streams. Piperazinones have further been found to be powerful stabilizers for materials subject to ultraviolet light degradation.
There exists several methods for the preparation of N-substituted piperazinones. U.S. Pat. No. 2,649,450 describes a process wherein a carbonyl compound, hydrogen cyanide and an ethylenediamine are reacted in the presence of water to yield a 1,4-dialkylpiperazin-2-one. This process is disadvantageous in that it requires the use of highly toxic hydrogen cyanide. The intermediate cyanohydrin of this process is also slow to rearrange to the final product.
U.S. Pat. No. 4,167,512 describes two syntheses for preparing poly-substituted 2-keto-1,4-diazacycloalkanes. One synthesis involves reacting a 1,2-diamine with a cyanohydrin in the presence of an organic solvent, an aqueous alkali, an onium salt catalyst and a haloform. The other method disclosed in U.S. Pat. No. 4,167,512 involves reacting a 1,2-diamine with a monoketone or monoaldehyde and a haloform reactant in the presence of an organic solvent, an aqueous alkali and an onium salt catalyst. These syntheses are disadvantageous in that the intermediates produced in these syntheses require severe conditions for conversion to the desired products. Thus, these syntheses are not as economical as desired.
What is needed is a toxic-free and straightforward process for preparing N-substituted piperazinones in a high yield. Such a process would allow the efficient production of N-substituted piperazinones which are useful in the removal of toxic contaminants from various industrial gases. The piperazinones so produced could also be used as stabilizers for materials susceptible to ultraviolet light degradation.